What is the best material for making gears?

  • #1

Main Question or Discussion Point

For making gears as light and strong as possible, what is the best material to use?
 

Answers and Replies

  • #2
11,483
5,009
Probably nylon. I know choice of material is sometimes dictated by possible failure modes. At college, our physics machinist maintained the school clock tower.

He used a brass gear at one juncture realizing if the clock hands froze in winter then this gear would shear sparing a possible catastrophic binding of the whole clock mechanism.
 
  • #3
OmCheeto
Gold Member
2,114
2,499
Probably nylon. ....
hmmm..... I'm not familiar with any cars with nylon transmission gears. :biggrin:
 
  • #4
CWatters
Science Advisor
Homework Helper
Gold Member
10,529
2,295
They have other requirements such as low wear rates that the OP didn't mention.
 
  • #5
CWatters
Science Advisor
Homework Helper
Gold Member
10,529
2,295
There are lots of different "nylons" some are reinforced with other materials. Some even contain lubricants.
 
  • #6
CWatters
Science Advisor
Homework Helper
Gold Member
10,529
2,295
Last edited by a moderator:
  • #7
russ_watters
Mentor
19,402
5,547
Since we are just guessing I'll add titanium while also saying that the constraint seems odd.
 
  • #8
11,483
5,009
hmmm..... I'm not familiar with any cars with nylon transmission gears. :biggrin:
Duh, how about model cars? :-)

Also, I didn't see where the OP mentioned cars in his/her post.
 
  • #9
Baluncore
Science Advisor
2019 Award
7,412
2,452
The biggest saving in weight is probably gained through using gears with several teeth in contact at the time, say an internal gear with a spur gear inside. Consider also Novikov or High-Conformal Gearing. That will also reduce the weight.

You could always cut smaller gears from a diamond with a laser.
 
  • #11
Nugatory
Mentor
12,614
5,165
hmmm..... I'm not familiar with any cars with nylon transmission gears. :biggrin:
But nylon timing gears were once quite common, before the widespread adoption of timing chains.

Really, the "what is the best material for a gear?" question has no better answer than "It depends." All else being the same, stronger and lighter is better, but we also have to consider factors such as cost, expected lifetime, lubrication requirements, sound properties, acceptable backlash, ......
 
  • #12
OmCheeto
Gold Member
2,114
2,499
But nylon timing gears were once quite common, before the widespread adoption of timing chains.

Really, the "what is the best material for a gear?" question has no better answer than "It depends." All else being the same, stronger and lighter is better, but we also have to consider factors such as cost, expected lifetime, lubrication requirements, sound properties, acceptable backlash, ......
And size.

Biggest gear I could find: 271 inch diameter [22.6 ft or 6.88 meters]
Smallest gear I could find: smaller than some horrible looking bug

For making gears as light and strong as possible, what is the best material to use?
Sameh, can you please let us know how big your gears are going to be. And perhaps, the torque requirements?
I've been looking for a reverse gear for a bicycle for several years, and as far as I can tell, no one makes one.
So I'm going to have to make one myself. So the answer to your question will probably help me also. Thanks!

ps. I don't recall seeing any bicycle gears made of nylon either. hmmm..... Guessing we're going to need to know if rocks and sticks and pant legs are going to be going through the gears. Ugh! Why does science have to be so complicated?
 
  • #13
CWatters
Science Advisor
Homework Helper
Gold Member
10,529
2,295
  • #14
Baluncore
Science Advisor
2019 Award
7,412
2,452
But nylon timing gears were once quite common, before the widespread adoption of timing chains.
Unless Nylon or polymer gears are saturated with the right type of oil they will absorb water and other oil components which makes them swell by several percent during use.

Engines once used long trains of metal timing gears. They were heavy and noisy and would typically break teeth when an engine backfired. The capacitor in the magneto or distributor fails, so the timing gear train catastrophically consumes it's teeth.

Laminated composite gears made from fibre reinforced phenol polymers were used because they were lighter weight and were quieter, but the teeth wore down and the gear needed replacing. Laminated gears were substituted by light weight alloy gears that tended to bruise more quickly, or were brittle and fractured.

Steel timing chains were used but stretched as wear accumulated. Chains were noisy and heavy so they clatter when cold and fly out against the spring loaded tensioner blocks.

Stepped rubber belts were then used because they were light weight and quiet with longitudinal fibres to control stretch. But they have a limited life, so if you do not replace them, the engine loses phase and smashes the pistons against the valves, which today economically writes off the vehicle.

There is no one perfect solution to timing control in 4-stroke reciprocating engines.
Likewise, there is no perfect gear material or design. Lighter weight = less reliable = shorter life.
 
  • #15
russ_watters
Mentor
19,402
5,547
OP has not been back to clarify, so the thread is locked.
 

Related Threads on What is the best material for making gears?

Replies
3
Views
705
Replies
10
Views
11K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
13
Views
2K
  • Last Post
Replies
3
Views
3K
Replies
5
Views
2K
Replies
7
Views
684
Replies
2
Views
578
Replies
3
Views
1K
  • Last Post
Replies
13
Views
3K
Top